In an automobile industry, a precision equipment industry, or the like, inhibition technique of transmission of vibration is required. It is advantageous that natural frequency of system having an object and a support portion be set sufficiently lower than a predetermined frequency range in inhibition technique of transmission of vibration. In this technique, the spring constant of the support portion may be small. However, in this case, deflection amount of spring may be large, and the spring may be large.
Techniques have been proposed in which a coned disc spring is disposed between the object and the support portion. Load characteristics of the coned disc spring can be designed as shown by a curved line in FIG. 10, so that a region A, at which the coned disc spring can support a load and the spring constant thereof can be set small, can be set.
However, when the coned disc spring deforms so as to be almost flat by application of load, an inner periphery portion and an outer periphery portion of the coned disc spring slides on counter members, so that friction generates therebetween. Due to this, when the use range of the coned disc spring is set within the region A in FIG. 10, in practical load characteristics of the coned disc spring, hysteresis shown in FIG. 11A generates. As a result, a substantial dynamic spring constant becomes a gradient of diagonal line 1 connecting the plot P and the plot Q in FIG. 11A. In this case, when amplitude of the use range is small, the dynamic spring constant is large.
As described above, in the conventional coned disc spring, when minimal amplitude vibration such as high-frequency vibration is input, dynamic spring constant of coned disc spring is large, so that transmission of high-frequency vibration cannot be inhibited. This problem is serious in the coned disc spring which deforms such that surface contact occurs between a counter member and a bending portion, which is provided at the inner peripheral edge portion and the outer peripheral edge portion of the coned disc spring, as disclosed in Japanese Unexamined Patent Application Publication No. H5-172171. In order to prevent generation of hysteresis in load characteristics, a low frictional member may be provided to at least one of spaces between the coned disc spring and the counter member as disclosed in Japanese Unexamined Patent Application Publication No. 2002-54685. However, in this technique in Japanese Unexamined Patent Application Publication No. 2002-54685, since the low frictional member, which is other than the coned disc spring, is provided, the number of parts is increased.
When the coned disc spring is uneven in the height direction, height adjustment is necessary. In order to solve this problem, upper and lower surfaces may be ground so as to perform height adjustment. However, in this case, when upper and lower surfaces may be ground, load characteristics greatly change, and inner and outer diameters change, so that bump occurs in providing the coned disc spring between an object and a support portion of system. In particular, in coned disc springs, inner and outer diameters of coned disc spring are determined as a design value beforehand depending on a system to which coned disc spring is provided. Due to this, in practice, height adjustment cannot be performed.